Solar energy constitutes a substantially inexhaustible replacement for fossil fuels which are limited in supply and relatively expensive to acquire. Many efforts have been made to develop solar energy devices and techniques and some of these are shown in various U.S. Patents, as well as in commercial developments and projects. Some of the U.S. Patents which relate to the subject of solar energy include U.S. Pat. Nos. 3,022,781; 3,991,742; 4,038,976; 4,059,094; 4,143,644; 4,146,012; 4,150,659 and Re 30,136.
S. Andrassy in U.S. Pat. No. 3,022,781 shows a solar fluid heating unit having two flexible film members secured to each other adjacent their peripheries and further secured to each other in preselected regions interiorly of the periphery to provide a fluid passageway between the two flexible film members. It is stated that the fluid passage may be serpentine or in the form of a pair of headers with a plurality of fluid conduits interconnecting the headers.
D. Gerber in U.S. Pat. No. 3,991,742 shows a heat transfer system utilizing solar energy and especially suitable for heating large quantities of water by small temperature increments by circulating the water in repeated cycles in a thin layer between two flexible sheets of a dark flexible panel. A pump supplies a continous quantity of water to be warmed to the upper edge of the panel and a distributor pipe evenly distributes the water along the top edge of the panel, wherefrom it flows over the member for spreading the water evenly over the entire surface area of the inside of the panel. A collector pipe collects the water at the bottom edge of the panel and a return system recirculates the warmed water to a pool therefor.
H. Stout et al. show in U.S. Pat. No. 4,038,967 a light-weight low-cost solar heating collecting system for use with homes and other such structures. A liquid black body medium is pumped to an elevated end of each unit and drains down through each panel by gravity feed back to a storage tank where the heated liquid is circulated on demand through the associated building. Each heating panel is comprised of a rigid foam plastic frame having a back wall on which is disposed a reflective stratum. A sheet of plastic material having a black surface is bonded to the reflective stratum along spaced parallel lines to define a plurality of parallel channels extending lengthwise of the panel. Manifolds are provided at opposite ends of the panel to feed the liquid into and drain the liquid from the channels.
C. Barrio de Mendoza shows in U.S. Pat. No. 4,059,094 a solar collector energy apparatus wherein is employed a parabolic reflective surface or mirror for receiving solar radiation and focusing the same onto a pipe disposed at the focal point of the reflecting arrangement. The pipe is also in direct contact with the parabolic mirror collector so as to receive reflection from the mirror. A heat chamber is included behind the parabolic mirror collector to trap heat behind the collector and provide an additional heat source for the pipe and for fluid therein.
H. Heitland et al. show a solar heating apparatus with a tubular conduit structure having an inlet and outlet for a flowable heat carrying medium and being formed of two elongated flexible foils, one being adapted to absorb solar radiation, the foils being sealingly connected along lines in their center regions to form a plurality of parallel flow channels which extend along the longitudinal axis of the foils. Transfer flow channels are provided which connect the respective ends of the parallel flow channels together.
W. Elkins et al. in U.S. Pat. No. 4,146,012 disclose a solar heat exchange panel manufactured by a high-speed rotogravure or heat sealing process wherein two elongated sheets of flexible plastic film are laminated together along lines defining inlet and outlet mainfolds and a plurality of flow passages. The manifolds extend substantially along the entire length of the sheets and the flow passageways are arranged in groups to form individual heat exchange sections which are served by the manifold. Mounting loops are provided along the lateral edges of the panel and are adapted for receiving elongated rods by which the panel can be coupled or secured to another such panel.
Bruce Buckley discloses in U.S. Pat. No. 4,150,659 an arrangement for venting the glazing or transparent cover of a solar collector in order to prevent the collector's absorber surface from reaching too high a temperature. The arrangement involves a damper at one end of the apparatus which is movable between positions which selectively permit communication between the air space in the associated solar energy collecting apparatus and ambient atmosphere and a particular arrangement is provided for undergoing thermally produced dimensional change in response to changing temperature conditions in the apparatus to move the damper between positions to allow air flow through the apparatus when the temperature exceeds a certain limit.
A. Schriefer shows in U.S. Pat. No. Re. 30,136 a solar collector for use in receiving solar raiation and converting the same to heat and including a matrix of plural layers of slit-and-expanded sheets contained within the solar collector with the heat produced by the matrix being transferred by convection into a force fluid flow. The surfaces of the slit-and-expanded sheets are coated to absorb and convert the radiant energy to heat and a reflective surface is provided behind the matrix to reflect solar energy back into the matrix.
I am furthermore aware of projects at Brookhaven National Library (BNL) in Upton, L.I., N.Y., funded by the Department of Energy and Environment, with the purpose of attempting to cut drammatically the cost of so-called flat plate solar collectors. These projects are believed to cover the details necessary to the actual construction of a production version of a thin-film collector that would be acceptable for mass installation.
The final working models of these projects, which were submitted for independent testing, certification and public exhibit, consisted of an absorber plate constructed of a laminate material consisting of 0.002 aluminum and 0.001 Teflon (FEP). The aluminum was bonded to the Teflon with an adhesive. The two layers were bonded with strips of pressure sensitive adhesive, placed in a manner which caused the perimeter to be sealed (and water-tight) and the intervening area to be divided into lanes which were deemed requisite to the "wetting" of the film. Holes were placed in one of the laminate skins communicating with each of the water lanes whereupon a pipe, drilled with identically spaced holes was put in place with adhesive in a manner which caused its holes to be aligned with the holes in the laminate skin thereby creating a mainfold entry for fluid to pass into or out of the absorber. This process occurred at both ends of the laminated absorber "bag" so as to provide an inlet and exhaust for a circulating fluid. The aluminum foil was then coated with material of a nature which enabled it to absorb more of the sun's rays than it re-radiated (otherwise known as a "selective" surface). Various paints could function well from an adhesion standpoint but the selective surface was chosen for its superior thermal performance despite the fact that it was supplied in sheet form which had to be bonded to the laminate by an adhesive medium. The reasoning behind the usage of aluminum foil was based upon the fact that entrapped air bubbles were inevitable in a gravity fed vessel constructed of opposed film structures. These bubbles will, if allowed to remain, hamper the overall effectiveness of an absorber due to the lack of utilization of the surface that is located over any such areas.